Stereo adaptor for import

I'm trying to fit a stereo and can't seem to get hold of the right parts to fix the car leads to the stereo. The problem is that the fitting coming from the car does not fit in the standard Toyota adaptor. Has anyone else got their hands on the correct fitting for an import model and if so, where can I get one? I'm in UK and it has been suggested that the fitting is similar to that needed for a Lexus and that it is available stateside online. Any ideas. I have taken some pics (not great quality) of the parts that need to fit in if that helps anyone...